Lithosphericstructure of the Central Andes based ona 3D gravimetric model

Abstract

We developed a 3Ddensity model of the conti nental crust, the subducted plate and the uppermantle of the Central Andes between 20-29°S and 74-61°W through theforward modelling of Bouguer anomaly. The goal of this contribution is to gaininsight on the lithospheric structure of the area, integrating the availableinformation (geophysical, geologic, petrologic, and geochemical) in a singlemodel. The geometry of our model is defined and constrained by hypocenterslocation, reflection and refraction seismic lines, travel time and attenuationtomography, receiver function analysis, magnetotelluric studies, thermal modelsand structural cross sections. The densities allocated to the different bodieswere calculated considering petrologic and geochemical data and pressure andtemperature conditions. The model consists of 31 parallel E-W vertical planes,where the continental crust comprises distinct bodies, which represent thedifferent morphotectonic units of the Central Andes.Contour maps of the depth to the top of the subducted plate, the depth of thecontinental Moho and the depth to the top of the asthenosphere below South America were produced. The residual anomaly was calculated bysubtracting from the Bouguer anomaly the gravimetric effect of the modelledsubducted slab and of the modelled Moho. This study demonstrates how 3D gravitymodelling, integrating geophysical, geologic and petrologic information, canhelp to reveal the lithospheric structure of the Central Andes.